Angiographic injector with pump motor starting control

ABSTRACT

The angiographic injector disclosed herein employs a pump motor which is gradually and progressively energized to prevent whipping of the catheter tip. The energization of the motor is varied as a function of a control signal voltage which rises relatively gradually, the motor being energized from an a.c. source through a triggerable semiconductor current switching device whose firing angle is varied as a function of the amplitude of the control signal voltage.

United States Patent Williamson 1451 July 4, 1972 [$4] ANGIOGRAPHICINJECTOR WITH PUMP MOTOR STARTING CONTROL [72] Inventor: Donald E.Williamson, Miami, Fla.

[73] Assignee: Coulis Corporation, Miami, Fla.

[22] Filed: July 13, 1970 [21] Appl.No.: 54,430

[52] 0.5. CI. ..l28/2 A, 128/218 A, 128/01, 318/599 51 Int. Cl. ..A61b5/02 [58] measures ..128/2 A,2R,2.05 F,2.05 R,

128/218 A, DIG. 1, 13; 318/599, 684, 227, 345; 331/111; 328/185;307/263, 265, 301, 315

[56] References Cited UN lTED STATES PATENTS 3,415,419 12/1968 Jewett etal ..128/2l8 A 3,573,580 4/1971 Shinozaki ..3 18/227 3,156,236 11/1964Williamson. .l28/2.05 R 3,192,449 6/1965 Brockett.. ..307/315 3,571,6963/1971 Liska ..307I301 3,447,055 5/1969 Mason ..3 18/345 3 ,192,4626/1965 James ..318/345 Primary Examiner-William E. Kamm Attorney-Kemvay,Jenney & Hildreth [57] ABSTRACT The angiographic injector disclosedherein employs a pump motor which is gradually and progressivelyenergized to prevent whipping of the catheter tip. The energization ofthe motor is varied as a function of a control signal voltage whichrises relatively gradually, the motor being energized from an a.c.source through a triggerable semiconductor current switching devicewhose firing angle is varied as a function of the amplitude of thecontrol signal voltage.

2 Claims, 3 Drawing Figures PATENTEUJUL 41m 3. 674.009

SHEET 1 or 2 oo m JJ mod 20 4:: E P E i c958 E glL FIG.|

INVENTOR DONALD E.WHiJAMSON BY WHM ATTORNEYS RIO INVENTOR DONALD E.WILLIAMSON B ATTORNEYS ANGIOGRAPIIIC INJECTOR WITH PUMP MOTOR STARTINGCONTROL BACKGROUND OF THE INVENTION This invention relates to anangiographic injector and more particularly to such an injectorproviding an injection pressure which rises relatively gradually therebyto prevent whipping of the catheter tip.

Angiographic injectors are employed in studying the functioning of apatients arterial system. The purpose of the injector is to introduce,through a long, thin, hollow catheter, materials which are radio-opaque,that is, which will provide contrast for X-ray photography. Typically,the catheter is introduced into the arterial system through a vesselwhich passes relatively close to the patientss skin so as to minimizethe insertion wound. The catheter is then threaded by the surgeon tothat part of the arterial system under study. Typically, it is desirablethat the injection of material be relatively precisely controlled intime so that synchronization of the injection with the X-ray photographyor with the patient's heart heat can be provided. Accordingly, incertain circumstances it may be necessary to employ relatively highinjection pressures. In various applications, however, a rapid onset ofa relatively high injection pressure will cause the tip of the catheterto whip, that is, to move violently sideways in an oscillatory motionwhich continues for the duration of the injection. This motion isobjectionable and may itself cause injury.

According to one aspect of the present invention, it has been found thatthe occurrence of this whipping motion can be eliminated by a relativelygradual application of pressure, even though relatively high pressuresare ultimately reached. This progressive application of the pressurecauses the tip of the catheter to move relatively slowly against thewall of the cavity or vessel in which it is positioned and to then beheld there as the pressure increases.

Among the several objects of the present invention may be noted theprovision of an angiographic injector in which injection pressure buildsup relatively gradually; the provision of such an injector in which therate of pressure build-up may be controlled and adjusted; the provisionof such an injector in which the ultimate pressure level is readilyadjustable; the provision of such an injector which prevents catheterwhipping; the provision of such apparatus which is highly reliable andwhich is relatively simple and inexpensive. Other objects and featureswill be in part apparent and in part pointed out hereinafter.

SUMMARY OF THE INVENTION The angiographic injector of the presentinvention employs an electric motor to pump radiosopaque materialthrough a catheter which is adapted to be inserted into a patient'svascular system. Whipping of the tip of the catheter is prevented bygradually and progressively energizing the motor at the start of aninjection cycle. The motor is connected to an 21.0. power source througha triggerable semiconductor current switching device so that theenergization of the motor is variable as a function of the phase angleof triggering of the switching device. A control signal voltage isgenerated which rises gradually over a plurality of cycles of the ac.source frequency, starting at a preselectable time. Further, means areprovided for repetitively triggering the switching device at a phaseangle which varies as a function of the amplitude of the control signalvoltage, the phase angle being progressively advanced. Accordingly, themotor is progressively energized and whipping of the catheter tip isprevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a somewhat diagrammaticillustration of an angiographic injector according to the presentinvention;

FIG. 2 is a schematic circuit diagram of motor control apparatusemployed in the FIG. 1 injector; and

FIG. 3 is a graphical representation of various waveforms occurring inthe circuit of FIG. 2.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis indicated at 11 generally, the mechanical injector assembly employedin the illustrative embodiment of apparatus constructed in accordancewith the present invention. This assembly may, for example, beessentially the same as that disclosed in my earlier U.S. Pat. No.3,156,236. For the purposes of the present invention it may be brieflynoted that this assembly comprises a piston pump I3, an electric motor15 for driving the pump, and a low friction ball-nut assembly 17 forconverting the rotary motion of motor 15 to a linear motion suitable foroperating the piston of the pump. The pump 13 provides radio-opaquecontrast material to an elongate catheter 14 for injection into apatients vascular system in conventional manner.

As is disclosed in the aforementioned patent, motor 15 is preferably ofthe permanent split capacitor type, although other motors adaptable tothis kind of operation can be used. At speeds substantially belowsynchronous speed, the permanent split type of motor provides asubstantially constant output torque for a given level of energization.Thus, the injection pressure may be controlled as a predictable andcontrollable function of energization of the motor 15. While an electricmotor has been illustrated as a preferred means of providing anelectrically controllable force, an electrically operated clutch orsolenoid may also be used as a force control, e.g. in conjunction with aseparate mechanical or hydraulic power source. Thus, as used herein, theterm motor means should be understood in its broad sense to include suchequivalents.

In accordance with the present invention, the energization of motor 15is controlled by means of a substantially conventional solid-state motorpower controller 19. Motor control I9 is of the type which employs atn'ggerable semiconductor eurrent-switching device, e.g. asilicon-controlled rectifier (SCR) or a triac. Such power controls areknown in the art and, accordingly, are not described in detail herein.As is understood in the art, the level of energization of motor 15 canbe controlled as a function of the phase angle of firing of thetriggersble current-switching device. Triggering pulses suitable forfiring such a current-switching device are applied to the motorcontroller 19 through a pulse transfonner TI from a programmablefiring-angle control 21. As will be described in greater detailhereinafter, control 21 includes a switch S1 whose operation controlsthe duration of an injection cycle and a variable resistance R8 forcontrolling the rate at which pressure is built up in the injector pump13. Control 2| may also include various timers and reversing switches(not shown) for controlling the operation of motor 15 as is conventionalin this art.

In the firing angle control 21 illustrated in FIG. 2, ac. power isapplied to a bridge rectifier DI through the switch S1. The pulsatingdc. voltage provided by the bridge D1 is applied, through a pair ofdropping resistors RI and R2, to a Zener diode D2 so as to provide,between a pair of leads L3 and L4, a clipped waveform substantially asillustrated at A in FIG. 3.

The firing angle control employs a relaxation oscillator which comprisesa unijunction transistor ()2. The base-one circuit of this transistor isconnected to the primary winding of pulse transformer T1, asillustrated. The base-two terminal of unijunction transistor 02 isconnected, through a load resistor R3, to the junction between droppingresistors RI and R2. This intermediate connection of the unijunctiontransistor somewhat spoils the regulation to transistor 02 provided bythe Zener diode D2, with regard to the operation of the relaxationoscillator, in a manner tending to compensate for the effect of linevoltage variation upon the operation of the motor 15.

The relaxation oscillator also comprises a timing capacitor C2 whichreceives charging current from two sources, a resistor R4 which isconnected to the positive supply lead L3 and the emitter output terminalof a Darlington pair amplifier Ql. The collectors of the Darlington pairare connected to the positive supply lead through a common load resistorR5 As is understood by those skilled in the art, the unijunctiontransistor 02 is a form of voltage breakdown device and when the voltageon capacitor C2 reaches the firing threshold which is determined by thetransistors intrinsic standoff ratio, the transistor fires, dischargingthe timing capacitor and delivering a pulse to the primary winding oftransformer Tl.

A voltage divider comprising a pair of resistors R6 and R10 and apotentiometer R9 is connected across the supply leads L3 and L4 forproviding a voltage which is a preselectable por tion of the totalpulsating dc. voltage. A current which is proportional to thispreselected voltage portion is applied, through the variable resistanceR8, to a capacitor C1. As is described hereinafter, the rate of chargingof capacitor C1 determines the rate at which pressure builds up in theinjector. The voltage on capacitor C1 is applied, through acurrentlirniting resistor R7, to the input terminal of the Darlingtonpair amplifier Q1.

The operation of this apparatus is substantially as follows. It isassumed initially that switch St is open and has been open long enoughso that the timing capacitors Cl and C2 are substantially discharged.Upon closing the switch S], the ac. supply voltage is applied to themotor and motor power controller but no current flows through the motorcircuit until triggering pulses are applied to the motor powercontroller 19. Since the capacitor C1 is initially discharged,substantially the only current available to charge capacitor C2 duringthe first ac half-cycle will be that provided through resistor R4.Accordingly, the voltage on capacitor C2 will reach the firing potentialof the unijunction transistor Q2 only toward the end of each achalf-cycle and thus the level of energization of motor will berelatively low.

Gradually, however, the voltage on capacitor C1 will rise, turning onthe Darlington pair and causing it to provide a component of chargingcurrent to the capacitor C2 during a portion of each half cycle. Thevalue of this component is determined essentially by the value ofresistor R5, the Darlington amplifier being operated in saturation. Thisadded component of charging current is provided, during each half cycle,until the voltage on capacitor C2 substantially reaches the level of thevoltage on capacitor C1, the base-emitter offset voltages being ignored,since at this point the Darlington pair turns off. From this point onuntil the unijunction transistor fires, the charging current is providedsubstantially only by the resistor R4. The waveform generated acrosscapacitor C2 is represented at B in FIG. 3 and it can be seen that thiswaveform has a break or knee at a point which varies from cycle to cycleas capacitor C1 charges. From FIG. 3 it can further be seen that, ascapacitor C1 charges, the unijunction transistor ()2 reaches its firingpoint, designated E earlier in each a.c. half-cycle. Accordingly, themotor power controller 19 is progressively fired at earlier phaseangles. As the energization of the motor 15 is thus gradually andprogressively increased, following the closing of switch S1, it can alsobe seen that the pressure in the injector will gradually andprogressively rise starting from the initiation of an injection cycle.After the unijunction transistor fires in each half cycle, it is kept inconduction for the rest of the half cycle by current provided throughthe Darlington pair 01 and then turned off at the end of the half cyclewhen the pulsating voltage provided by the bridge rectifier Dl drops tozero. In this way, the charging of capacitor C2 starts from a repeatablestarting point for each half cycle.

Since the charging current provided to capacitor Cl is variable as afunction of the setting of rheostat R8, the rate at which pressureincreases following initiation can be adjusted by varying the setting ofthis rheostat. If only a predetermined rate of rise is needed, a fixedresistance may be used in place of rheostat R8.

In view of the foregoing, it may be seen that several objects of thepresent invention are achieved and other advantageous results have beenattained. 4

As various changes could be made in the above construction withoutdeparting from the scope of the invention, it should be understood thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is: 1. An angiographic injector comprising: a catheteradapted to be inserted into a patients vascular system; a pump forpropelling radio-opaque material through said catheter; an electricmotor for driving said pump; at least one semiconductor current controldevice; means for connecting said motor means to an electric powersource through said current control device so that the energization ofsaid motor means is controllably variable; means for generating acontrol signal having an amplitude which varies in accordance with apredetermined gradual time function having a preselectable timeconstant, starting at a controllable point in time, said generatingmeans including means for adjusting said time constant; means forvarying the conduction of said current control device as a function ofsaid control signal to progressively energize said motor means andthereby prevent whipping of the catheter tip. 2. An angiographicinjector comprising: a catheter adapted to be inserted into a patientsvascular system; a pump for propelling radio-opaque material throughsaid catheter; an electric motor for driving said pump; at least onetriggerable semiconductor current switching device; means for connectingsaid motor to an ac power source through said current switching deviceso that the energization of said motor is variable as a function of thephase angle of triggering of said switching device relative to thephasing of the source power; a first capacitor; means for applying apreselectable d.c. charging current to said first capacitor when saidmotor is energized thereby to generate a control signal voltage whichchanges gradually over a plurality of cycles of said a.c. source, saidcharging current applying means including means for manually adjustingthe value of said charging current; a timing capacitor; means forapplying a first charging current component to said timing capacitor;means for applying a second charging current component to said timingcapacitor when the timing capacitor voltage is below said control signalvoltage; and a voltage breakdown device interconnected with said timingcapacitor to generate a pulse for firing said triggerable semiconductorcurrent switching device within each half cycle of the source a.c. whenthe voltage on said timing capacitor reaches a predetermined value, thephase angle of firing being progressively advanced relative to thephasing of the source power, whereby said motor is progressivelyenergized and whipping of the catheter tip is prevented.

1. An angiographic injector comprising: a catheter adapted to beinserted into a patient''s vascular system; a pump for propellingradio-opaque material through said catheter; an electric motor fordriving said pump; at least one semiconductor current control device;means for connecting said motor means to an electric power sourcethrough said current control device so that the energization of saidmotor means is controllably variable; means for generating a controlsignal having an amplitude which varies in accordance with apredetermined gradual time function having a preselectable timeconstant, starting at a controllable point in time, said generatingmeans including means for adjusting said time constant; means forvarying the conduction of said current control device as a function ofsaid control signal to progressively energize said motor means andthereby prevent whipping of the catheter tip.
 2. An angiographicinjector comprising: a catheter adapted to be inserted into a patient''svascular system; a pump for propelling radio-opaque material throughsaid catheter; an electric motor for driving said pump; at least onetriggerable semiconductor current switching device; means for connectingsaid motor to an a.c. power source through said current switching deviceso that the energization of said motor is variable as a function of thephase angle of triggering of said switching device relative to thephasing of the source power; a first capacitor; means for applying apreselectable d.c. charging current to said first capacitor when saidmotor is energized thereby to generate a control signal voltage whichchanges gradually over a plurality of cycles of said a.c. source, saidcharging current applying means including means for manualLy adjustingthe value of said charging current; a timing capacitor; means forapplying a first charging current component to said timing capacitor;means for applying a second charging current component to said timingcapacitor when the timing capacitor voltage is below said control signalvoltage; and a voltage breakdown device interconnected with said timingcapacitor to generate a pulse for firing said triggerable semiconductorcurrent switching device within each half cycle of the source a.c. whenthe voltage on said timing capacitor reaches a predetermined value, thephase angle of firing being progressively advanced relative to thephasing of the source power, whereby said motor is progressivelyenergized and whipping of the catheter tip is prevented.